UniSA researchers have developed a low-cost method for delivering safe drinking water to millions of vulnerable people by utilizing low-cost, sustainable materials and sunlight. Fresh water accounts for less than 3% of the world’s water supply, and due to the pressures of climate change, pollution, and shifting population patterns, this already scarce resource is becoming scarcer in many areas.
Currently, 1.42 billion people, including 450 million children, live in areas of high or extremely high water vulnerability, a figure that is expected to rise in the coming decades. Researchers at the University of South Australia’s Future Industries Institute have developed a promising new process that could eliminate water stress for millions of people, including those in many of the world’s most vulnerable and disadvantaged communities.
A team led by Associate Professor Haolan Xu has refined a technique for obtaining freshwater from seawater, brackish water, or contaminated water via highly efficient solar evaporation, producing enough daily fresh drinking water for a family of four from just one square metre of source water.
Researchers have developed technology that could eliminate water stress for millions of people, including those living in many of the planet’s most vulnerable and disadvantaged communities.
“There has been a lot of interest in using solar evaporation to create fresh drinking water in recent years,” Assoc Prof Xu says. “However, previous techniques have been too inefficient to be practically useful.” “We’ve overcome those inefficiencies, and our technology can now deliver enough freshwater to meet a wide range of practical needs at a fraction of the cost of existing technologies like reverse osmosis.”
A highly efficient photothermal structure sits on the surface of a water source and converts sunlight to heat, focusing energy precisely on the surface to rapidly evaporate the uppermost portion of the liquid.
While other researchers have investigated similar technology, previous efforts have been hampered by energy loss, with heat passing into the source water and dissipating into the surrounding air. “Previously, many experimental photothermal evaporators were basically two-dimensional; they were just a flat surface, and they could lose 10 to 20% of solar energy to the bulk water and the surrounding environment,” explains Dr. Xu.
While other researchers have investigated similar technology, previous efforts have been hampered by energy loss, with heat passing into the source water and dissipating into the surrounding air. “Previously, many experimental photothermal evaporators were basically two-dimensional; they were just a flat surface, and they could lose 10 to 20% of solar energy to the bulk water and the surrounding environment,” explains Dr. Xu.
In contrast to other researchers’ two-dimensional structures, Assoc Prof Xu and his team created a three-dimensional, fin-shaped, heatsink-like evaporator. Their design directs excess heat away from the top surfaces of the evaporator (i.e. the solar evaporation surface), distributing it to the fin surface for water evaporation, cooling the top evaporation surface, and achieving zero energy loss during solar evaporation.
Because of the heatsink technique, all surfaces of the evaporator remain cooler than the surrounding water and air, allowing additional energy to flow from the higher-energy external environment into the lower-energy evaporator. “We are the world’s first researchers to extract energy from bulk water during solar evaporation and use it for evaporation, which has helped our process become efficient enough to deliver between 10 and 20 liters of fresh water per square meter per day.”
Aside from its efficiency, the system’s practicality is enhanced by the fact that it is constructed entirely of simple, everyday materials that are low cost, sustainable, and easily accessible. “Because one of the main goals of our research was to deliver for practical applications, the materials we used were simply sourced from the hardware store or supermarket,” Assoc Prof Xu explains.
“The only exception is photothermal materials, but even there we use a very simple and cost-effective process, and the real advances we have made are in system design and energy nexus optimization, not materials.”
The system is not only simple to build and deploy, but it is also simple to maintain because the design of the photothermal structure prevents salt and other contaminants from accumulating on the evaporator surface. Because of the low cost and ease of maintenance, Assoc Prof Xu and his team’s system could be deployed in situations where other desalination and purification systems would be financially and operationally unviable.
“For example, in remote communities with small populations, the infrastructure cost of systems like reverse osmosis is simply too high to ever justify,” Assoc Prof Xu says. “However, our technique could deliver a very low-cost alternative that would be easy to set up and basically free to run.”
Furthermore, because it is so simple and requires almost no maintenance, no technical expertise is required to keep it running, and maintenance costs are minimal. This technology has the potential to provide long-term clean water solutions to people and communities who cannot afford other options, and these are the places where such solutions are most desperately needed.
In addition to drinking water applications, Assoc Prof Xu says his team is currently investigating a variety of other applications for the technology, such as wastewater treatment in industrial operations. “There are a lot of potential ways to adapt the same technology,” he says, “so we are really at the start of a very exciting journey.”
